﻿// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

// This was copied from https://github.com/dotnet/runtime/blob/39b9607807f29e48cae4652cd74735182b31182e/src/libraries/System.Private.CoreLib/src/System/Diagnostics/CodeAnalysis/NullableAttributes.cs
// and updated to have the scope of the attributes be internal.
namespace System.Diagnostics.CodeAnalysis
{
#if !NETCOREAPP

	/// <summary>Specifies that null is allowed as an input even if the corresponding type disallows it.</summary>
	[AttributeUsage (AttributeTargets.Field | AttributeTargets.Parameter | AttributeTargets.Property, Inherited = false)]
	internal sealed class AllowNullAttribute : Attribute { }

	/// <summary>Specifies that null is disallowed as an input even if the corresponding type allows it.</summary>
	[AttributeUsage (AttributeTargets.Field | AttributeTargets.Parameter | AttributeTargets.Property, Inherited = false)]
	internal sealed class DisallowNullAttribute : Attribute { }

	/// <summary>Specifies that an output may be null even if the corresponding type disallows it.</summary>
	[AttributeUsage (AttributeTargets.Field | AttributeTargets.Parameter | AttributeTargets.Property | AttributeTargets.ReturnValue, Inherited = false)]
	internal sealed class MaybeNullAttribute : Attribute { }

	/// <summary>Specifies that an output will not be null even if the corresponding type allows it.</summary>
	[AttributeUsage (AttributeTargets.Field | AttributeTargets.Parameter | AttributeTargets.Property | AttributeTargets.ReturnValue, Inherited = false)]
	internal sealed class NotNullAttribute : Attribute { }

	/// <summary>Specifies that when a method returns <see cref="ReturnValue"/>, the parameter may be null even if the corresponding type disallows it.</summary>
	[AttributeUsage (AttributeTargets.Parameter, Inherited = false)]
	internal sealed class MaybeNullWhenAttribute : Attribute
	{
		/// <summary>Initializes the attribute with the specified return value condition.</summary>
		/// <param name="returnValue">
		/// The return value condition. If the method returns this value, the associated parameter may be null.
		/// </param>
		public MaybeNullWhenAttribute (bool returnValue) => ReturnValue = returnValue;

		/// <summary>Gets the return value condition.</summary>
		public bool ReturnValue { get; }
	}

	/// <summary>Specifies that when a method returns <see cref="ReturnValue"/>, the parameter will not be null even if the corresponding type allows it.</summary>
	[AttributeUsage (AttributeTargets.Parameter, Inherited = false)]
	internal sealed class NotNullWhenAttribute : Attribute
	{
		/// <summary>Initializes the attribute with the specified return value condition.</summary>
		/// <param name="returnValue">
		/// The return value condition. If the method returns this value, the associated parameter will not be null.
		/// </param>
		public NotNullWhenAttribute (bool returnValue) => ReturnValue = returnValue;

		/// <summary>Gets the return value condition.</summary>
		public bool ReturnValue { get; }
	}

	/// <summary>Specifies that the output will be non-null if the named parameter is non-null.</summary>
	[AttributeUsage (AttributeTargets.Parameter | AttributeTargets.Property | AttributeTargets.ReturnValue, AllowMultiple = true, Inherited = false)]
	internal sealed class NotNullIfNotNullAttribute : Attribute
	{
		/// <summary>Initializes the attribute with the associated parameter name.</summary>
		/// <param name="parameterName">
		/// The associated parameter name.  The output will be non-null if the argument to the parameter specified is non-null.
		/// </param>
		public NotNullIfNotNullAttribute (string parameterName) => ParameterName = parameterName;

		/// <summary>Gets the associated parameter name.</summary>
		public string ParameterName { get; }
	}

	/// <summary>Applied to a method that will never return under any circumstance.</summary>
	[AttributeUsage (AttributeTargets.Method, Inherited = false)]
	internal sealed class DoesNotReturnAttribute : Attribute { }

	/// <summary>Specifies that the method will not return if the associated Boolean parameter is passed the specified value.</summary>
	[AttributeUsage (AttributeTargets.Parameter, Inherited = false)]
	internal sealed class DoesNotReturnIfAttribute : Attribute
	{
		/// <summary>Initializes the attribute with the specified parameter value.</summary>
		/// <param name="parameterValue">
		/// The condition parameter value. Code after the method will be considered unreachable by diagnostics if the argument to
		/// the associated parameter matches this value.
		/// </param>
		public DoesNotReturnIfAttribute (bool parameterValue) => ParameterValue = parameterValue;

		/// <summary>Gets the condition parameter value.</summary>
		public bool ParameterValue { get; }
	}

#endif

#if !NETCOREAPP || NETCOREAPP3_1

	/// <summary>Specifies that the method or property will ensure that the listed field and property members have not-null values.</summary>
	[AttributeUsage (AttributeTargets.Method | AttributeTargets.Property, Inherited = false, AllowMultiple = true)]
	internal sealed class MemberNotNullAttribute : Attribute
	{
		/// <summary>Initializes the attribute with a field or property member.</summary>
		/// <param name="member">
		/// The field or property member that is promised to be not-null.
		/// </param>
		public MemberNotNullAttribute (string member) => Members = new[] { member };

		/// <summary>Initializes the attribute with the list of field and property members.</summary>
		/// <param name="members">
		/// The list of field and property members that are promised to be not-null.
		/// </param>
		public MemberNotNullAttribute (params string[] members) => Members = members;

		/// <summary>Gets field or property member names.</summary>
		public string[] Members { get; }
	}

	/// <summary>Specifies that the method or property will ensure that the listed field and property members have not-null values when returning with the specified return value condition.</summary>
	[AttributeUsage (AttributeTargets.Method | AttributeTargets.Property, Inherited = false, AllowMultiple = true)]
	internal sealed class MemberNotNullWhenAttribute : Attribute
	{
		/// <summary>Initializes the attribute with the specified return value condition and a field or property member.</summary>
		/// <param name="returnValue">
		/// The return value condition. If the method returns this value, the associated parameter will not be null.
		/// </param>
		/// <param name="member">
		/// The field or property member that is promised to be not-null.
		/// </param>
		public MemberNotNullWhenAttribute (bool returnValue, string member)
		{
			ReturnValue = returnValue;
			Members = new[] { member };
		}

		/// <summary>Initializes the attribute with the specified return value condition and list of field and property members.</summary>
		/// <param name="returnValue">
		/// The return value condition. If the method returns this value, the associated parameter will not be null.
		/// </param>
		/// <param name="members">
		/// The list of field and property members that are promised to be not-null.
		/// </param>
		public MemberNotNullWhenAttribute (bool returnValue, params string[] members)
		{
			ReturnValue = returnValue;
			Members = members;
		}

		/// <summary>Gets the return value condition.</summary>
		public bool ReturnValue { get; }

		/// <summary>Gets field or property member names.</summary>
		public string[] Members { get; }
	}

#endif
}